People often say that the problem with string theory is that it doesn't make any prediction, but that's not quite right: the problem is that it can make almost any prediction you want it to make. It is really less of a "theory" in its own right and more of a mathematical framework for constructing theories.
One day some unusual observation will come along from somewhere, and that will be the loose end that allows someone to start pulling at the whole ball of yarn. Will this happen in our lifetimes? Unlikely, I think.
The problem is that once, a long time ago, String Theory was something that made concrete predictions that people just couldn't calculate.
Then people managed to calculate those predictions, and they were wrong. So the people working that theory up relaxed some constraints and tried again, and again, and again. So today it's that framework that you can use to write any theory you want.
That original theory was a good theory. Very compelling and just a small adjustment away from mainstream physics. The current framework is just not a good framework, it's incredibly hard to write any theory in it, understand what somebody else created, and calculate the predictions of the theories you create.
I am old enough to remember when string theory was expected to explain and unify all forces and predict everything. Sadly, it failed to deliver on that promise.
And there is no known single real world experiment that can rule out string theory while keeping general relativity and quantum mechanics intact.
More accurately, string theory is not wrong (because it just cannot be wrong). Because it does not predict anything and cannot invalidate anything, it does not help to advance our understanding of how to integrate general relativity and quantum mechanics.
It should not be called theory - maybe set of mathematical tools or whatever.
You can't really show it's wrong because there are dozens of different theories but using the Wikipedia definition "point-like particles of particle physics are replaced by one-dimensional objects called strings" it's possible that particles are not strings. I guess it would then be like fairies at the end of the garden theory. Good from a literary fiction point of view but not reality.
string boot framework
I was planning to make a similar comment. Conjecturing that some theory in the string theory landscape [0] gives a theory of quantum gravity consistent with experiments that are possible but beyond what humans may ever be capable of isn't as strong of a claim as it may first appear. The intuition I used to have was that string theory is making ridiculously specific claims about things that may remain always unobservable to humans. But the idea is not that experiments of unimaginable scale and complexity might reveal that the universe is made up of strings or something, it's just that it may turn out that string theory makes up such a rich and flexible family of theories that it could be tuned to the observed physics of some unimaginably advanced civilization. My impression is that string theory is not so flexible that its uninteresting though. There's some interesting theoretical work along these lines around exploring the swampland [1].
[0] https://en.wikipedia.org/wiki/String_theory_landscape
[1] https://en.wikipedia.org/wiki/Swampland_(physics)
Or, that day will never come, because string theory isn't reflective of the actual world, or because there are so many theories possible under the string theory rubric that we can never find the right one, or because the energies involved to see any effect are far beyond what could be reached in experiment.
It isn't completely implausible that a future civilisation could perform the experiments to gather that data, somehow; but it is hard to envisage how we do it here on Earth.
Your implicit point is a good one. Is it sensible to have a huge chunk of the entire theoretical physics community working endlessly on a theory that could well end up being basically useless? Probably not.
There is not a "huge chunk" of the theoretical physics community working on string theory, and their never was. For one, it is far less common a topic of research now then it was earlier when it was more popular, but even then "huge" was really "a lot of universities had a grant for string theory investigation because it looked promising".
It mostly hasn't worked out and now people are moving on to other things.
The single worst thing that happened though was the populism: a small group of people with credentials started putting out pop-sci books and doing interviews, well in excess of what their accomplishments should mean. People are like "so many people are working on this" because there were like, 3 to 5 guys who always said "yes" to an interview and talked authoritatively.
Huge is a subjective term, but go and count the number of participants at Strings 2025 [1]. Then realise that is just one of many conferences [2]. It's still a very big field.
[1] https://nyuad.shorthandstories.com/strings-conference-abu-dh...
[2] https://www.stringwiki.org/wiki/Conferences
A meaningless statement if you aren't going to introduce any points of comparison. But I would hardly call 735 conference participants a huge conference. Like, that's big but there are lot more then 735 theoretical physicists.
Claude tells me that there are about ~5000 theoretical high energy physicists actively publishing as tracked by INSPIRE-HEP (the de facto search engine in that field). If we estimate that about a third or half of string theorists take part in Strings in a given year -- because there are other big conferences like String Pheno that will be more relevant for many -- then we have something like 30-50% of high energy theorists working on string theory.
I agree that people should be "moving on to other things," but I'm not seeing the evidence that they actually are.
Are all the attendees of a Linux conference Linux developers? Are all the people who attend CCC penetration testers?
> the problem is that it can make almost any prediction you want it to make
In logic this is either the principle of "contradiction elimination" or a "vacuous truth". Depending on how you look at it. i.e. given sufficiently bad premises, you can prove anything.
> less of a "theory" in its own right and more of a mathematical framework for constructing theories.
so it's javascript?
Theorists are real good at bending around experimental data, unusual or not